The present invention relates to an apparatus and method for drilling holes in electronic circuit substrates using laser light.
FIG. 7 schematically shows the construction of a known laser processing apparatus, such as a CO2 gas laser machining apparatus. Laser light 102 emitted from a laser oscillator 101 is guided onto a workpiece 107 for forming micropores therein. A galvanometer 104 swings as it reflects received laser light 102 onto an fxcex8 lens 105 in a scanning manner. Thereupon, the fxcex8 lens 105 converges the incident rays to form a focus spot 106 at a predetermined location on the workpiece 107.
In general, laser light emitted from such laser oscillator contains light rays of various wavelengths and of various intensities. For achieving a high degree of precision in laser machining, the presence of light of various differing wavelengths presents a problem, particularly when employing an fxcex8 lens, which is highly liable to chromatic aberration.
That is, when the laser light, which contains a plurality of light rays having different wavelengths xcex1, xcex2, xcex3, is emitted toward the fxcex8 lens, chromatic aberration tends to occur because of the differences in wavelength of the laser light, since the refraction index of the fxcex8 lens differs depending on the wavelength. As a result, a plurality of focus spots are respectively formed by the discrete light rays of various wavelengths, as indicated by reference designators f1, f2, and f3 in FIG. 7. This is particularly so when the light incident position is spaced from the center of the fxcex8 lens. The formation of a plurality of focus spots f1, f2, and f3 leads to unfavorable drilling results such as oval holes or a plurality of separate holes.
The present invention has been devised in light of the above-described problems encountered by the prior art, and it is an object of the invention to provide an improved laser processing method and an apparatus therefor, with which the formation of a plurality of or oval focus spots is inhibited, and drilling of favorable shapes is ensured.
A laser processing apparatus according to the invention includes:
a laser oscillator for emitting laser light;
an fxcex8 lens positioned relative to the laser oscillator for converging the emitted laser light onto a workpiece; and
a wavelength selector interposed between the laser oscillator and the fxcex8 lens for separating a light ray having a specified wavelength out of the laser light.
By providing the wavelength selector between the laser oscillator and the fxcex8 lens, a light ray having a specified wavelength is singled out from the laser light. The single light ray converged by the fxcex8 lens forms only a single focus spot. Thus adverse effects of chromatic aberration caused by the fxcex8 lens are eliminated, whereby the formation of deformed focus spots or a plurality of focus spots is inhibited, and the machining precision is enhanced.
These and other objects and characteristics of the present invention will become further clear from the following description with reference to the accompanying drawings.